Design of MySQL DB to avoid having a table with mutually exclusive fields

Question

I'm creating a new DB and I have this problem: I have two type of users that can place orders: registered users (that is, they have a login) and guest users (that is, no login). The data for registered users and guest users are different and that's why I'm thinking of using two different tables, but the orders (that share the same workflow) are all the same, so I'm thinking about using only one table.

I've read here and here (even if I don't understand fully this example) that I can enforce a MySQL rule to have mutually exclusive columns in a table (in my case they'd be "idGuest" and "idUser") but I don't like that approach.

Is there a better way to do it?

Answer 1

There are several approaches, which depends on the number of records and number of unique fields. For example, if you would say they differ in only two fields, I would have suggested that you just put everything in the same table.
My approach, assuming they differ a lot, would be to think "objects":
You have a main user table, and for each user type you have another table that "elaborates" that user info.

Users
-----

id,email,phone,user_type(guest or registered)

reg_users
---------

users_id, username,password etc.....

unreg_users
-----------

user_id,last_known_address, favorite_color....etc

Where user_id is foreign key to users table